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Biomedical subjects

K Kobashi

Publications and source records attributed to K Kobashi.

At least 145 records · Page 8Linked to original sources
PubMed1986

Concentrations of metallothionein and metals in malignant and non-malignant tissues in human liver.

Concentration of metallothionein in the malignant and non-malignant tissues of the human liver was determined by the Cd-hem method. The concentration of metallothionein was high in the non-malignant tissue (471 +/- 306 micrograms/g). Metallothionein in the non-malignant tissue was mainly Zn-thionein and metallothionein-bound Zn was a major chemical form of Zn in the non-malignant tissue. The concentration of metallothionein in the malignant tissue was 75.6 +/- 79.6 micrograms/g, and significantly lower than that in the nonmalignant tissue. A strong, positive relationship was observed between the Zn and metallothionein concentrations, and the regression equation was MT (microgram/g) = -94.7 + 11.9 Zn (micrograms/g).

Adult↗
PubMed1986

3 beta-Hydroxysteroid dehydrogenase of Ruminococcus sp. from human intestinal bacteria.

Ruminococcus sp. PO1-3 obtained from human intestinal flora is able to reduce dehydrocholate as well as 3-ketoglycyrrhetinate. From this bacterium dehydrocholate- and 3-ketoglycyrrhetinate-reducing activities were purified one thousand-fold together with 3-ketocholanate-reducing and 3-beta-hydroxyglycyrrhetinate (glycyrrhetic acid) oxidizing activities by means of Matrex Red A, Sephadex G-200 and Octyl-Sepharose column chromatography. The purified enzyme catalyzed the reduction of dehydrocholic acid to 3 beta-hydroxy-7,12-diketocholanic acid and of 3-ketocholanic acid to 3 beta-hydroxycholanic acid. Studies on substrate specificity revealed that the enzyme had absolute specificity for the beta-configuration of a hydroxyl group at the 3 position of bile acid and steroids having no double bond in the A/B ring. This enzyme was neither beta-hydroxysteroid dehydrogenase [EC 1.1.1.51] nor 3 beta-hydroxy-delta 5-steroid dehydrogenase [EC 1.1.1.145], but a novel type of enzyme, defined as 3 beta-hydroxysteroid dehydrogenase.

3-Hydroxysteroid Dehydrogenases↗
PubMed1986

[An in vitro chemosensitivity study using human tumor clonogenic assay in urologic malignancies].

A soft agar colony formation assay, so called human tumor clonogenic assay (HTC assay) similar to that originally described by Salmon and colleagues, was utilized to measure the sensitivity of a total of 85 urologic malignancies including 36 urothelial cell carcinomas, 41 renal cell carcinomas, 5 testicular tumors, and 3 Wilms' tumors to anticancer drugs. In addition, the results obtained were compared with those of a novel dye exclusion method (NDE assay) described by Weisenthal and colleagues. The NDE assay was utilized to measure the sensitivity of a total of 63 urologic malignancies including 28 urothelial cell carcinomas, 25 renal cell carcinomas, 6 testicular tumors, and 4 Wilms' tumors to anticancer agents. In both assay series, the concentration of anticancer drugs tested was approximately one tenth of the maximum serum level achievable after single bolus injection. The colony forming rate inhibition of 70% or more in the HTC assay and the cell survival rate of 30% or less in the NDE assay were defined as "sensitive." Sixteen of the 36 urothelial cell carcinomas, 11 of the 41 renal cell carcinomas, and 1 of the 5 testicular tumors had both more than 30 colonies grown in control plates and enough cells in the specimens to provide at least one drug sensitivity testing. In urothelial cell carcinomas, 3 out of 13 tumors were "sensitive" to adriamycin, 3 out of 16 to cis-platinum, and 4 out of 15 to carboquone. In renal cell carcinomas, 2 out of 9 tumors were "sensitive" to adriamycin, 4 out of 11 to vinblastine, and none of 4 to Interferon alpha.(ABSTRACT TRUNCATED AT 250 WORDS)

Antineoplastic Agents↗
PubMed1985

A colorimetric method for the determination of hydroxamic acid by iodine oxidation.

A new colorimetric method for the determination of hydroxamic acid is described. Hydroxamic acid was oxidized quantitatively by iodine to produce nitrous acid, which was thereafter determined according to the diazocoupling reaction. This method is sensitive to as little as 5 nmol of hydroxamic acid, and the calibration curve is linear up to 50 nmol. Using this method, acyl-CoAs were determined after conversion to hydroxamic acid by the addition of hydroxylamine. The present method is applicable to the determination of free fatty acids which are activated by acyl-CoA synthetase.

Chemical Phenomena↗
PubMed1985

Aldose reductase inhibitors: flavonoids, alkaloids, acetophenones, benzophenones, and spirohydantoins of chroman.

The inhibitory activity of various compounds, including 12 flavonoids, 10 alkaloids, 15 benzophenones, 5 acetophenones, and 7 spirohydantoins of chroman, was tested on rabbit lens aldose reductase, an enzyme involved in complications of diabetes. Almost all compounds tested were found to inhibit the enzyme at low concentrations (10(-5) M). The most potent inhibitor was 2R,4S-6-chloro-2-methylspiro(chroman-4,4'-imidazo-lidine+ ++)-2',5'-dione with an I50 value of 4.7 x 10(-8) M; other spirohydantoins showed similar potency. Polyhydroxybenzophenones were also potent inhibitors with an I50 value of about 10(-7) M. The possible structure-inhibitory activity relationships of the compounds tested are discussed.

Acetophenones↗
PubMed1985

Specific inhibition of urease by N-acylphosphoric triamides.

Benzoyl- and isopentenoyl phosphoric triamides (BPA and IPA) strongly inhibited urease activities from jack bean, soybean, watermelon seed, Proteus mirabilis, P. rettgeri, P. vulgaris, Mycobacterium smegmatis, and Ureaplasma urealyticum. Their I50 values (the final concentration causing 50% inhibition), independent of enzyme source, were 2-21 nM, which are about 1,000-fold lower than that of caprylohydroxamic acid, one of the most potent urease inhibitors. ATP-urea amidolyase activity was inhibited 50% by BPA at a higher concentration of 0.28 mM, but was not affected by IPA even at 1.3 mM. Thirteen kinds of hydrolases (trypsin, chymotrypsin, thermolysin, leucine aminopeptidase, papain, lipase, alpha-amylase, glucuronidase, asparaginase, arylsulfatase, alkaline phosphatase, acid phosphatase, and true cholinesterase), two oxidoreductases (catalase and alcohol dehydrogenase), three transferases (glutamic-oxaloacetic aminotransferase, gamma-glutamyl transpeptidase, and arylsulfotransferase) and two kinases (pyruvate kinase and creatine kinase) were not affected at all even at 1 mM BPA and IPA. Exceptionally, pseudo-cholinesterase from human serum was inhibited by BPA and IPA, whose I50 values were 70 nM and 10 muM, respectively, using acetylthiocholine as a substrate. These values increased to 0.55 muM and 54 muM, respectively, when acetylcholine was used as a substrate. These results show that N-acylphosphoric triamides potently and specifically inhibit urease activity at concentrations of nM order.

Amidohydrolases↗
PubMed1985

Cystinosis with marked atrophy of the kidneys and thyroid. Histological and ultrastructural studies in an autopsy case.

The eldest autopsied case (a 23-year-old man) of infantile form of cystinosis with uremia and myxoedema was reported. The cystine content per gram wet tissue of various organs was arranged as follows: the thyroid (4.61 mg), kidney (1.71 mg), eye (0.75 mg), spleen (0.65 mg), liver (0.49 mg), and brain (0.016 mg). In polarized light microscopy, cystine crystals were detected in the epithelial cells and epithelial lumina of both kidneys by Wollaston test, and foam cells with cystine crystals were histologically found in the reticuloendothelial and other organs, especially in the bone marrows. Moreover, electron microscopic findings revealed square, rectangular or lozenge-shaped small cystine crystal profiles in osmophilic dense bodies of the histiocytic cells and in the cytoplasm of the foam cells. In some of them, positive reaction for acid phosphatase activity was specifically localized at the periphery of the cystine crystal profiles.

Adult↗
PubMed1985

Enzymatic reduction of sennidin and sennoside in Peptostreptococcus intermedius.

Peptostreptococcus intermedius, one of the dominant bacteria of human intestine, reduced sennidin and sennoside to rheinanthrone and 8-glucosyl-rheinanthrone, respectively, and these reduction rates were stimulated by the addition of nicotinamide adenine dinucleotide (reduced form) (NADH), flavin adenine dinucleotide (FAD) and glucose. The reduction was accelerated by removing oxygen from the incubation tubes, which indicates the inhibition of the reduction by O2. Thus, for the maximal activity, the reaction system required an anaerobic condition and cofactors, NADH and FAD. This bacterium also reduced methyl orange, whose mode of reduction resembled that of sennidin reduction. More than 80% of these activities were recovered in the supernatant fraction after sonication of the bacterial suspension, and these activities were purified together by means of Sephadex G-200 gel-filtration and diethylaminoethyl-cellulose column chromatography. The purified enzyme reduced FAD and benzyl viologen in the presence of NADH under an anaerobic condition.

Anthracenes↗
PubMed1984

Change in kinetic property of M1-type pyruvate kinase from hyperbolic type to sigmoidal type by limited proteolysis with an acid fraction from rabbit liver.

An acid extract of rabbit liver contained M1-type pyruvate kinase inactivating activity, and was separated to three fractions. The optimal inactivation of the enzyme with Fraction II (Mr 42,000) was observed at pH 5.5, and this inactivation was completely prevented by leupeptin and antipain, but not by pepstatin. With Fraction III (Mr 22,000), on the other hand, optimal inactivation of the enzyme was observed at pH 8-9, and was not prevented by these inhibitors. The kinetic properties, with phosphoenolpyruvate, of the enzyme were changed from hyperbolic type to sigmoidal type by the limited proteolysis with Fractions II and III. The subunit molecular weight of the enzyme (57,300) was decreased to 55,800 via 56,400 in the former case and to 56,400 in the latter case.

Animals↗
PubMed1984

Modification of thiol groups of Jack bean urease with diazonium-1H-tetrazole.

Jack bean urease [EC 3.5.1.5] was modified with diazonium-1H-tetrazole (DHT). Reaction of DHT with the enzyme produced a characteristic absorption peak at 320 nm and led to complete loss of the enzymatic activity at a low concentration of DHT. Amino acid analysis of DHT-modified urease showed that only cysteine residues reacted with the reagent and other amino acid residues such as tyrosine, histidine, and lysine did not. The enzymatic activity was protected against DHT-inactivation by the addition of substrate. On the other hand, when the cysteine residues were modified with DHT, the enzyme was not converted to polymeric forms. Furthermore, the binding ability of urease with hydroxamic acid, a specific urease inhibitor, was virtually unaffected by DHT-inactivation. These results indicate that cysteine residues are specifically modified by DHT with concomitant loss of enzymatic activity and polymerization ability, but are not essential for the binding of hydroxamic acid to the enzyme.

Amino Acids↗
PubMed1984

Photo-oxidation of histidine residues in rat M1- and L-type pyruvate kinases.

Rat M1- and L-type pyruvate kinases were inactivated by photo-oxidation mediated by methylene blue at pH 8.0 and O degrees C according to first-order kinetics. The pH profiles of the inactivation rates of these isozymes showed that amino acid residues having a pK value of 7.0-7.5 were involved in the inactivation. Three histidine residues per subunit of M1- or L-type enzyme were destroyed by the photo-oxidation with complete loss of the enzyme activities. However, two of the three photo-oxidized histidine residues in the L-type enzyme were more important in the inactivation reaction. The kinetics of the partially inactivated L-type enzyme suggests that complete inactivation is achieved via an intermediate form having low affinity for phosphoenolpyruvate (PEP). These observations revealed the involvement of essential histidine residues of two different kinds in the catalytic mechanism of the L-type enzyme. In the photo-oxidation of M1-type enzyme, no intermediate form was observed. Addition of PEP or pyruvate to the reaction mixture markedly prevented the photo-oxidative inactivation of only the M1-type enzyme in the presence of K+ and Mg2+; the addition of ADP or ATP was ineffective even in the presence of both metal ions. This protective effect of PEP was counteracted by further addition of ATP but not by ADP. However, photo-oxidative inactivation of the L-type enzyme was not prevented even by the addition of PEP in the presence of both metal ions, owing to the low affinity for PEP at 0 degrees C, in spite of the presence of fructose 1,6-bisphosphate (Fru-1,6-P2).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Amino acid sequence around a cysteine residue in the active center of jack bean urease.

Cysteine residues in the active center of jack bean urease [EC 3.5.1.5] were modified with 14C-labeled diazonium-1H-tetrazole (DHT). The labeled enzyme was carboxymethylated with iodoacetic acid, and then hydrolyzed with trypsin. The tryptic digest was subjected to gel filtration on Sephadex G-50, yielding two radioactive fractions. The [14C]DHT-labeled peptide having a lower molecular weight, which was determined to be approximately 1,000 by the method of gel filtration, was further purified to homogeneity by ion-exchange chromatography on DEAE-Sephadex A-25. [14C]DHT-labeled cysteine was identified as cysteic acid after performic acid oxidation, and the amino acid sequence of the low-molecular-weight [14C]DHT-labeled peptide was determined to be Phe-Glu-Pro-Gly-Asp-Cys-Asn-Ser-Thr-Phe-Lys.

Amino Acid Sequence↗
PubMed1984

Stone formation by Ureaplasma urealyticum in human urine and its prevention by urease inhibitors.

When Ureaplasma urealyticum T-960 was inoculated into normal human urine (10(8) viable cells per ml of urine), a white precipitate formed, with an increase in pH of the infected urine. This precipitate was identified as a mixture of struvite and whitelockite by analysis of the infrared spectrum. Its formation was completely prevented by the addition of 10 microM N-benzoylphosphotriamide, 20 microM N-isopentenoylphosphotriamide, or 0.5 mM caprylohydroxamic acid without the alkalinization of the urine, and the Ureaplasma color change units were also decreased markedly by these compounds. The apparent concentrations for 50% inhibition by N-benzoylphosphotriamide,N-isopentenolyphosphotriamide, and caprylohydroxamic acid against Ureaplasma urease were 7 nM, 2 nM, and 2.2 microM, respectively. From these results, it seems that stone formation by U. urealyticum is prevented with these compounds, that prevention being directly attributable to the inhibition of urease activity, which causes the death of the cells.

Bacteriuria↗